The present invention relates to methods for removing cholesterol from edible triglyceride fats and oils including animal fats, marine oils and vegetable oils, to prepare reduced cholesterol fats and oils.
Substantial research effort has been directed to removal of cholesterol from animal fats and egg products, as well as to the preparation of cholesterol-reduced food products which include animal fats such as milkfat and beef tallow, or egg products such as egg yolk as important functional constituents of the food product. A variety of techniques to remove cholesterol from animal fats, egg yolks and whole eggs have been proposed or utilized, but have various disadvantages. One approach would utilize microorganisms to enzymatically oxidize and degrade cholesterol [Japanese Patent 60-18375], but produces cholesterol oxidation products which may be undesirable. Organic solvents have also been used to extract cholesterol [JP 48/44458, U.S. Pat. Nos. 4,104,286, 3,881,034, 3,563,765, 4,234,619 and Tokarska, et al., Can. Inst. Food Sci. Tech. J., 18:256-258 (1985)], but such extraction methods tend to remove a substantial portion of the triglyceride oils, and may require extensive processing steps to remove after extraction solvents from the extracted product. Even with supercritical carbon dioxide as the solvent, selectivity of cholesterol over triglycerides may be limited [Prepared Foods, 157:186 (1988); JP 59/135847]. Edible vegetable oils such as soybean oil have also been used to extract cholesterol from egg yolks as described in U.S. Pat. Nos. 3,717,414, 4,103,040 and 4,333,959. However, such extractions produce a waste stream of spent cholesterol-containing vegetable oil. An economical process for regenerating this spent oil would accordingly be desirable.
U.S. Pat. No. 4,804,555 discloses a process for the simultaneous deodorization and cholesterol level reduction of fish oils. The fish oil is deaerated, mixed with steam, heated, flash vaporized, thin film-stripped with a countercurrent stream, and cooled. U.S. Pat. No. 4,234,619 discloses a method for cholesterol removal from eggs by dehydrating the eggs, extracting the cholesterol with liquid dimethyl ether under anhydrous conditions, and removing the dimethyl ether by treatment under reduced pressure at low temperatures. U.S. Pat. No. 4,104,286 describes the isolation of cholesterol from eggs through extraction with ethanol, saponification in an aqueous ethanolic alkali metal hydroxide, and concentration and purification with a hydrocarbon solvent and methanol. U.S. Pat. No. 4,393,044, describes the formation of a steroid ester to be used as an oil phase material or base material for cosmetics or ointments. However, such techniques each have various disadvantages, and improved methods for removing cholesterol from triglyceride oils would be desirable. Accordingly, it is an object of the present invention to provide new methods for removing cholesterol from fats and oils.